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Author Topic: turbo and injector size question  (Read 1896 times)
skihor
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« on: July 07, 2011, 04:21:19 PM »

In our '67 MC 5A I have a 6V92 350 HP with an Allison 5 speed automatic. This thing is got LOADS of power,
BUT, I just can't keep it cool. Everything is very well sealed, bigger blower wheels, new Rad cores, water pump, t-stats, smaller blower pulley, etc... My question is: Can I step down a size or two on the injectors and not change the turbo ? It has 9G90's in it now.

Don & Sheila
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skihor
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« Reply #1 on: July 08, 2011, 11:00:01 AM »

This question is on our other bus, not the one I'm having the injector timing issue with. This bus should have the "proper" 350 HP set-up. 9G90 injectors with a 1.08 turbo. I got the set-up from Jim Sheppard when he did his re-power. Jim correct me if I'm wrong. Anyway I've been trying to cool this beast for 7 years now, and I'm about to give up. So..... My question is: Can I drop the injecter size down a size or two and retain the same turbo ?? AND, if so, will that cut the heat production down much ?? Would anyone who can answer this also give me a HP rating along with the injector recommendation.

Much thanks guys,

Don & Sheila
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luvrbus
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« Reply #2 on: July 08, 2011, 11:36:01 AM »

Drop down to 9g75's set @ 1.460 you have 277 hp and the heat goes down ok and Tv7511 turbo should work,tell us what hp range you would like I don't ever go over 330 hp on those little engines myself.
You can have the 9g85's set at 1.466  with turbo Tv7511 A/R 108 you can have 300 hp,1015 ft lbs of torque @ 1800rpm not 2100 rpm like with the 9g90's . Brian I have no idea what hp your C was set from MCI but the old 8v71 in the  GreyHounds were 240 hp 

good luck
« Last Edit: July 08, 2011, 12:12:07 PM by luvrbus » Logged

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bevans6
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« Reply #3 on: July 08, 2011, 11:54:11 AM »

I'm guessing that it would cost around $1500 to change the injectors, unless you can install them and tune it up yourself.  Would another approach be to add a third radiator?  I've been thinking about two approaches for if I have a cooling problem with my new engine - add a third radiator in series with the one on the passenger side, plumb it into the  coolant pipe that runs down to the rail, and position it where the old AC compressor was, horizontal, with electric fans dumping air out the bottom (or even position it vertically and run a fan from the main pulley like that AC compressor drive belt was positioned), or second - put a radiator in the AC condensor bay plumbed into the piping for the OTR heat, and blow the air down under the floor.  Those ideas might cost about the same, but you'd keep your 350 hp.  270 hp in the 5 would feel like a stock 8V71 in bus tune...

Brian
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skihor
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« Reply #4 on: July 08, 2011, 01:01:50 PM »

I'm guessing that it would cost around $1500 to change the injectors, unless you can install them and tune it up yourself.  Would another approach be to add a third radiator?  I've been thinking about two approaches for if I have a cooling problem with my new engine - add a third radiator in series with the one on the passenger side, plumb it into the  coolant pipe that runs down to the rail, and position it where the old AC compressor was, horizontal, with electric fans dumping air out the bottom (or even position it vertically and run a fan from the main pulley like that AC compressor drive belt was positioned), or second - put a radiator in the AC condensor bay plumbed into the piping for the OTR heat, and blow the air down under the floor.  Those ideas might cost about the same, but you'd keep your 350 hp.  270 hp in the 5 would feel like a stock 8V71 in bus tune...

Brian

I have added TWO more rads equal to to stock ones. I mounted them behind the two lower louvered doors. I designed them with "tabs" top and bottom on one side and "pivot" mounted them. A third tab on the other side for a "latch". The system works great for access to the sides of the engine compartment, (filters and such). I put 3000 CFM electric fans on each one, pulling from the outside. Not much improvement. It's possible that I just destroyed a large source of fresh air into the engine compartment.  I'm beginning to think that this engine is more than 350 HP. This bus does haul a**. It will pull a 6% grade @ 55 or 60, (if the temp is @ 20* F) My next move will be cutting out the rear doors and installing expanded metal, and also, directing the exhaust flow from the blowers out the top of the rear doors instead of straight down into the engine compartment. I'm hoping to create some "draw" out of the engine compartment. I just can't see where I could put an air to air cooler in.

Don & Sheila
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Boomer
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« Reply #5 on: July 08, 2011, 05:09:58 PM »

If you have an after cooler and 100% mini bypass blower with 9G90's you will be around 370 hp if I remember correctly.  Take Cliffords advise and drop her back a few notches and lose the smoke too.
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« Reply #6 on: July 08, 2011, 05:14:26 PM »

Also, get out the Donaldson catalog and find the lowest back pressure 5" straight through muffler they have, and the highest CFM Eco series air filter.  Install these and wrap the exhaust from the turbo back, it helps.
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skihor
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« Reply #7 on: July 08, 2011, 08:51:56 PM »

Also, get out the Donaldson catalog and find the lowest back pressure 5" straight through muffler they have, and the highest CFM Eco series air filter.  Install these and wrap the exhaust from the turbo back, it helps.
Exhaust is wrapped all the way around, even to the muffler, have a large Freightliner air filter with 7" in,
 5" out, have the proper back pressure Donaldson muffler, (yes Detroit 2 strokes need some back pressure). I have also run it without the filter connected with no change in power or heat build.
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thomasinnv
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« Reply #8 on: July 08, 2011, 10:54:20 PM »

(yes Detroit 2 strokes need some back pressure)

not to derail this thread, but...a buddy has a 4905 with a 6v92, straight piped with no muffler. will the turbo provide necessary back pressure or is he looking for trouble? or is back pressure really even an issue?
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« Reply #9 on: July 09, 2011, 12:24:12 PM »

Don,

I thought the bigger injectors simply injected more fuel.  So were it me, and it isn't, I would want to know if smaller injectors would accomplish anything.  Can't you simply "set" the injectors to run injecting less fuel at WOT?  You do have a MUI. right?  If you ran the hills with a much lighter foot you would be making less HP and making fewer BTUs and it would "act" like the same engine with smaller injectors....right?

It takes a lot more power to run 50 MPH up a hill than it does to run 40 MPH.  That is the same effect that installing smaller injectors would have and the same benefit, I would think.

Do your "twin" temp gauges each read the same temp?  Both banks of the V6 running at the same temp?  How many degrees are the rads dropping the temp?

Is your torque converter locked up on the hill?

Run a straight out exhaust and see what that does for you.  make sure the run you try has few if any turns or 90s.

Have you tried removing the thermostats?

Are the impellers of both water pumps firmly on the drive shafts?

Coming off of a hard pull what does your rad(s) look like when shot with a IR heat gun?  Even between both rads?  Even across each rad form side to side?  In terms of heat rejection, what is the size of the rad? 

Stopping the air flow thru your engine compartment will not aid cooling.  Wrapping your manifolds and piping will most certainly aid, in some way, probably small, to cooling but the ROI is prohibitively small.

Good luck,  Lot of spit balling here on my part.


John
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luvrbus
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« Reply #10 on: July 09, 2011, 01:16:24 PM »

Over fueling a 2 banger they will run hot
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buswarrior
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« Reply #11 on: July 10, 2011, 04:26:36 PM »

Did you say that your added rads are attempting to blow OUT?

"pulling from the outside"

Turn them around to blow/suck IN the cool outside air.

I think you are fighting the natural suction at the back of the coach, instead of taking advantage of it?

To test for opening up the back with expanded metal, just wire the engine doors part way open and try it out.

With all that you have, you should be able to shed a lot of BTU's.

happy coaching!
buswarrior

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JohnEd
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« Reply #12 on: July 10, 2011, 05:13:29 PM »

Do you have the stock rads that are used with the 8V71?

John
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skihor
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« Reply #13 on: July 10, 2011, 06:48:31 PM »

Did you say that your added rads are attempting to blow OUT?

"pulling from the outside"

Turn them around to blow/suck IN the cool outside air.

I think you are fighting the natural suction at the back of the coach, instead of taking advantage of it?

To test for opening up the back with expanded metal, just wire the engine doors part way open and try it out.

With all that you have, you should be able to shed a lot of BTU's.

happy coaching!
buswarrior



Yes I set them to pull in cooler outside air. My concern is that I completely filled the lower louvered door openings with the extra rads, and that effectively eliminated any benefit of fresh air from there.  Fix one problem create another... I'm going to cut out the rear doors, put expanded metal in, and, direct the blower exhaust out towards the top of the doors thus creating some "pull" out of the engine compartment. I think exhausting the 200* air directly outside instead of contributing to the overall engine compartment heat will help. I have 3000 CFM fans on each of the new Rads drawing in fresh air. I have a few more ideas, one thing at a time. I know I'm trying to re-invent the wheel here but I LIKE this power, and I won't give in easily.

Don & Sheila
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lostagain
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« Reply #14 on: July 10, 2011, 06:54:33 PM »

I put big holes in the right engine floor pans. First trip this weekend. My temp stays cooler. So I will remove the pan entirely now. Air off the rad squirrel fans into the engine comp. flows out the bottom easier now. I have a third rad on the pass. side engine door, with electric fans drawing outside air through that rad and into the engine compartment. I am not sure if that helps.

MC5C, 6V92 with 90 inj., Allison HT740. It will smoke black with my foot to the floor. I drive it with my foot just off a bit so it doesn't smoke: that keeps it cool. In other words, you can manage the amount of fuel it gets with your foot. Cheaper than new injectors.

JC
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JC
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« Reply #15 on: July 10, 2011, 06:59:10 PM »

Don, why not try something simple.
GMC's used a single wide mudflap behind the rear axle that almost touched the ground. This effectively created a low pressure area at the bottom of the engine compartment which drew the hot air down and out the bottom.

Oh, and just a thought, if you happen to have across the rear bumper... remove it, you'll see a decrease in heat retention in the engine compartment.

Just a couple of Dinar's worth.

DF
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